<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <script language="javascript">
        //CharMode函数
        //测试某个字符是属于哪一类.
        function CharMode(iN) {
            if (iN >= 48 && iN <= 57) //数字
                return 1;
            if (iN >= 65 && iN <= 90) //大写字母
                return 2;
            if (iN >= 97 && iN <= 122) //小写
                return 4;
            else
                return 8; //特殊字符
        }

        //bitTotal函数
        //计算出当前密码当中一共有多少种模式
        function bitTotal(num) {
            modes = 0;
            for (i = 0; i < 4; i++) {
                if (num & 1) modes++;
                num /= 2;
            }
            return modes;
        }

        //checkStrong函数
        //返回密码的强度级别
        function checkStrong(sPW) {
            if (sPW.length <= 4)
                return 0; //密码太短
            Modes = 0;
            for (i = 0; i < sPW.length; i++) {
                //测试每一个字符的类别并统计一共有多少种模式.
                Modes |= CharMode(sPW.charCodeAt(i));
            }
            return bitTotal(Modes);
        }

        //pwStrength函数
        //当用户放开键盘或密码输入框失去焦点时，根据不同的级别显示不同的颜色
        function pwStrength(pwd) {
            O_color = "#eeeeee";
            L_color = "#FF0000";
            M_color = "#FF9900";
            H_color = "#33CC00";
            if (pwd == null || pwd == '') {
                Lcolor = Mcolor = Hcolor = O_color;
            } else {
                S_level = checkStrong(pwd);
                switch (S_level) {
                    case 0:
                        Lcolor = Mcolor = Hcolor = O_color;
                    case 1:
                        Lcolor = L_color;
                        Mcolor = Hcolor = O_color;
                        break;
                    case 2:
                        Lcolor = Mcolor = M_color;
                        Hcolor = O_color;
                        break;
                    default:
                        Lcolor = Mcolor = Hcolor = H_color;
                }
            }
            document.getElementById("strength_L").style.background = Lcolor;
            document.getElementById("strength_M").style.background = Mcolor;
            document.getElementById("strength_H").style.background = Hcolor;
        }
    </script>

</head>

<body>

<form>
    输入密码:<input type="password" size="10" onKeyUp="pwStrength(this.value)" onBlur="pwStrength(this.value)">
    <br>密码强度:
    <table width="217" border="1" cellspacing="0" cellpadding="1" bordercolor="#cccccc" height="20">
        <tr align="center" bgcolor="#eeeeee">
            <td width="33%" id="strength_L">弱</td>
            <td width="33%" id="strength_M">中</td>
            <td width="33%" id="strength_H">强</td>
        </tr>
    </table>
</form>

</body>
</html>